Generally, a substrate processing system includes a multiple number of process modules for performing a plasma process on a semiconductor wafer (hereinafter, simply referred to as a “wafer”) as a substrate by using plasma, and a transfer module for transferring a wafer between the process modules or between process modules and load lock modules for conveying a wafer (see, for example, Patent Document 1).
The process modules and the transfer module respectively have a depressurized inner space. The inner spaces of the process modules and the inner space of the transfer module are partitioned by opening/closing gate valves. Further, the transfer module has an extensible/contractible transfer arm. When the inner space of the process module and the inner space of the transfer module communicate with each other by opening the gate valve, the transfer arm enters the inner space of the process module and loads/unloads a wafer into and from the process module.
The wafer is held and transferred by the transfer arm. Recently, it is required to shorten a time for transferring the wafer in order to improve throughput of the plasma process on the wafer. That is, the wafer is kept on standby state in front of a closed gate valve by the transfer arm, and then, is loaded into the process module immediately after the gate valve is opened.
Patent Document 1: Japanese Patent Laid-open Publication No. 2009-212453 (FIG. 1)
However, when the gate valve is opened, a small amount of fine particles, e.g., particles having a diameter of several nm, may be produced by vibration caused by the opening motion of the gate valve or friction between the gate valve and another member.
Conventionally, although particles having a diameter of several nm adhere to a wafer, such particles cause only little adverse effects on the yield of semiconductor devices manufactured from the wafer. Recently, however, due to the miniaturization of wiring in semiconductor devices or the like, if particles having a diameter of several nm adhere to a wafer, semiconductor devices manufactured from the wafer is regarded as an inferior goods. Therefore, even if particles have a diameter of, e.g., several nm, it is necessary to prevent such particles from adhering to the wafer.